Voters now oppose Prop. 19, which would legalize marijuana, 49% to 44%, and Prop. 23, which would suspend the state's global warming law, 48% to 37%. The opposition has surged since September.

California voters have turned against controversial initiatives to legalize marijuana and to suspend the state's global warming law, a poll from the Public Policy Institute of California found.

Voters now oppose Proposition 19, the marijuana legalization measure, 49% to 44%, and the measure to halt a law that aims to cut greenhouse gas emissions, 48% to 37%.

The poll indicated that opposition has surged since September, when 52% of likely voters backed Proposition 19, which would allow Californians to grow and possess pot, and they split evenly over Proposition 23.

The earlier poll's Proposition 19 result had encouraged supporters and attracted some high-dollar donations. The measure would allow Californians who are 21 and older to grow and possess marijuana, while cities and counties could authorize commercial cultivation, sales and taxation.

The latest poll found support had eroded significantly across all demographic groups, but most steeply among Latino voters. In September, 63% backed it. Now, 51% oppose it.

Mark Baldassare, the organization's pollster, said the drop may have come because of a barely visible campaign. He noted that the proponents have to persuade voters that people like them support the initiative. "The burden of proof is always on the yes side," he said.

He also said that opponents seemed more passionate about the issue. Among likely voters who said the legalization issue was very important to them, 33% planned to vote for it and 63% against it.

Baldassare also said the poll found no indication that young people were more enthused about marijuana legalization than older voters. Democrats have started to talk about using the issue as a way to motivate young voters in 2012.

Much of the reversal appears to be driven by evaporating support in Southern California. In September, 56% of likely voters in Los Angeles County and 52% in other Southern California counties supported the measure. This month, those percentages slipped to 41% and 42%.

"As expected, California voters are taking a closer look at Prop. 19 and are just saying 'No,' " said Roger Salazar, a spokesman for the opposition. "While the measure claims to regulate, control and tax marijuana, voters don't need eyedrops to clearly see it does none of those things."

Tom Angell, a spokesman for Yes on 19, said the poll indicates that the race is close. "We'll be doing everything we can to get our message out, including working with a team of hundreds of committed volunteers who are spending their free time calling undecided voters," he said. "I don't think the other side can match that."

Proposition 23 would suspend the Global Warming Solutions Act, which was passed in 2006, until unemployment in the state drops to 5.5% for at least a year — a level that has rarely been achieved for that duration. Joblessness in the state is now more than 12%.

A statewide television blitz by opponents has painted the initiative as a "deceptive scheme" bankrolled by "two Texas oil companies." The companies, Valero Energy Corp. and Tesoro Corp., would "pollute our air, kill clean energy jobs and keep us addicted to costly oil," the TV spots charged.

The message may have resonated. "The voters are very cynical about initiatives," Baldassare said. "They assume that there is some interest group that is behind it unless they hear otherwise."

The opposition campaign, funded by Silicon Valley technology firms, national environmental groups and wealthy conservationists, has raised more than $28 million, while supporters raised $9 million. As its money dried up, the Yes campaign curtailed its TV campaign, which attacked the law as an "energy tax" that would kill jobs.

Steven Maviglio, a spokesman for No on 23, said, "Californians are seeing Prop. 23 for what it is: a deceptive measure financed by Texas oil companies to kill California's clean air and energy standards."

But Anita Mangels, spokeswoman for the proponents, said it is the ad campaign that is deceptive. "The poll is testimony to what can happen when billionaire hedge-fund managers and venture capitalists decide it's more in their self-interest to invest in defeating an initiative that would pull the plug on subsidies and incentives for 'green tech' than to invest in the green-tech sector itself," she said.

Education mattered more than income in the survey. Among likely voters with college degrees, 55% opposed Proposition 23, as opposed to 37% of those with a high school degree or less. But there was no significant difference between those earning more than $80,000 a year, or less than $40,000.

Proposition 23 has become a flashpoint in the gubernatorial and senatorial races. Democratic candidates Jerry Brown and Sen. Barbara Boxer strongly oppose it. Meg Whitman says she would suspend the global warming law for a year and try to "fix" it. Carly Fiorina supports Proposition 23.

The Public Policy Institute of California surveyed 1,067 likely voters Oct. 10-17. The poll has a margin of error of plus or minus 3.5 percentage points. The earlier survey was taken Sept. 19-26.